Android App Development is the process of building Android apps - software applications designed to run on smartphones or tablets using the Android operating system (OS).
The apps are usually written in the Java programming language or developers can download an Android software development kit (SDK) - see Android Developer Tools - directly from the Android website. This includes tools, sample code and other documents relevant to building Android apps.
The App Inventor is an online application that enables inexperienced developers to build an Android app.